Dell S4820T, Configuration Manual

Page: 462 / 1178

Link Dampening
Interface state changes occur when interfaces are administratively brought up or down or if an interface
state changes.
Every time an interface changes a state or flaps, routing protocols are notified of the status of the routes
that are affected by the change in state. These protocols go through the momentous task of re-
converging. Flapping; therefore, puts the status of entire network at risk of transient loops and black
holes.
Link dampening minimizes the risk created by flapping by imposing a penalty for each interface flap and
decaying the penalty exponentially. After the penalty exceeds a certain threshold, the interface is put in an
Error-Disabled state and for all practical purposes of routing, the interface is deemed to be “down.” After
the interface becomes stable and the penalty decays below a certain threshold, the interface comes up
again and the routing protocols re-converge.
Link dampening:
• reduces processing on the CPUs by reducing excessive interface flapping.
• improves network stability by penalizing misbehaving interfaces and redirecting traffic.
• improves convergence times and stability throughout the network by isolating failures so that
disturbances are not propagated.
Important Points to Remember
• Link dampening is not supported on VLAN interfaces.
• Link dampening is disabled when the interface is configured for port monitoring.
• You can apply link dampening to Layer 2 and Layer 3 interfaces.
• You can configure link dampening on individual interfaces in a LAG.
Enabling Link Dampening
To enable link dampening, use the following command.
• Enable link dampening.
INTERFACE mode
dampening
Examples of the
show interfaces dampening
Commands
To view the link dampening configuration on an interface, use the
show config
command.
R1(conf-if-te-1/1)#show config
!
interface TenGigabitEthernet 1/1
ip address 10.10.19.1/24
dampening 1 2 3 4
no shutdown
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Interfaces